Method of improving metal surfaces



Dec. 26, 1961 N. F. CALLAHAN, JR 3,014,274

METHOD OF IMPROVING METAL SURFACES Filed July 22, 1957 INVENTOI? NORMANI? CALLAHAIVJR.

United States Patent 3,014,274 METHOD OF IMPROVING METAL SURFACES NormanF. Caiiahan, In, Stevenson, Conn, assignor to United AircraftCorporation, East Hartford, Conn, a corporation of Delaware Filed July22, 1957, Ser. No. 673,265 1 Claim. (Cl. 29-556) This invention relatesto a method for forming a metal surface minimizing imperfections thereinand more particularly nonmetallic inclusions in the finished machinedsurface of cylindrical forgings.

An object of this invention is to form a metallic piece havingcorrugations on the area which is to be transformed into a smoothsurface. This piece may be a forged bar member with circumferentialcorrugations extending therearound.

Another object of this invention is to form a metallic piece in whichthe longitudinal grainflow thereof extends into the corrugations whichhave been formed thereon.

A further object of this invention is to form a smooth surface in whichthe surface contains ends of the metal grain by removing thecorrugations.

Another object of this invention is to set up a wavy grainflow extendinginto corrugations adjacent the surface to be formed to change theorientation of any nonmetallics in the metal so that their end crosssections will be exposed on the finished surface.

A surface of this type will expose only a small end 7 view of anonmetallic inclusion. This inclusion will then not appear as animperfection of objectionable size in certain inspection procedures.

Other objects and advantages will be apparent from the specification andclaims and from the accompanying drawings which show one embodiment ofthe invention.

FIG. 1 shows a shaft forged with circumferential corrugations extendingtherearound.

FIG. 2 is an enlarged section taken through a portion of the shaft shownin FIG. 1 revealing the longitudinal wavy grainflow extending into thecorrugations.

While FIG. 1 shows corrugations formed on a cylindrical or bar member,the corrugations may also be formed on pieces having other shapes. Thecorrugated shaft 2 shown in FIG. 1 can be formed from a metallic rodwhich has been forged or rolled or formed by some other desired method.To form the corrugations 4, a forging procms can be used with dieshaving corrugations set therein.

Upon completion of the corrugated shaft as shown in FIG. 1, thelongitudinal grainflow of the shaft has changed so that the grainflownow waves into the corrugations 4. This grainflow is shown in FIG. 2 byrepresentative lines 3,014,274 Patented Dec. 26, 1961 6. The extent towhich the grainflow extends into the corrugations depends on the widthof the corrugation and the depth of the corrugation. To provide a wavygrainflow having a suificient number of grmn lines flowing into thecorrugations, the depth of the corrugations and their width can becontrolled until a desired number are present.

To form a smooth metal surface, the circumferential corrugations areremoved to a depth below the lowest corrugation (see dot and dash lineA-A in FIG. 2). It can be seen from this figure that the cross sectionof any grain line which extended intothe corrugations would be exposedon the final surface. This surface can be formed by a machining off ofthe corrugations. However, this operation can be formed by the removalof the conugations by other satisfactory means. The material on which asurface can be formed by the methoddisclosed herein is any material ofgranular structure which can be formed with corrugations and having thegrain flow into the corrugations.

It is to be understood that the invention is not limited by the figuresherein illustrated and described but may be used otherwise withoutdeparture from its scope as defined in the following claim.

I claim:

A method of making a metal shaft having a surface containing end crosssections of grain flow to control nonmetallic inclusions in a shaftsurface from a metal susceptible of being forged which comprises;forging stock to form a shaft having a plurality of circumferentialadjacent corrugations extending therearound with a wavy grain flow whichflows into the corrugations; while forging, the depth of thecorrugations and their width being controlled to provide a wavy grainflow having a willcient number of grain lines so that when thecorrugations are removed the surface contains end cross sections of thewavy grain flow; and then removing the corrugations to a depth to exposeend cross sections of the wavy grain flow on the finished surface of theshaft to reduce the length of grain flow appearing on the surface.

References Cited in the file of this patent UNITED STATES PATENTS HildSept. 22, 1959

